EP3405738A1

EP3405738A1 - Method for connecting tubes of a tube bundle heat exchanger to a tube plate of the tube bundle heat exchanger

Info

Publication number: EP3405738A1
Application number: EP17701792.8A
Authority: EP
Inventors: Christoph Seeholzer; Georg Wimmer
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2016-01-19
Filing date: 2017-01-18
Publication date: 2018-11-28
Anticipated expiration: 2037-01-18
Also published as: CN108474634A; EP3405738B1; RU2018124245A3; CN108474634B; RU2718393C2; WO2017125253A1; US20190017757A1; RU2018124245A

Abstract

The present invention relates to a method for connecting tubes (125) of a tube bundle heat exchanger to a tube plate (130) of the tube bundle heat exchanger, wherein the tubes (125) are cohesively connected to the tube plate (130) by laser welding, during the course of which a laser beam (211) is generated and is focused on a location to be welded in a connecting region (250) between tube (125) and tube plate (130), wherein the laser beam (211) is moved so as to perform a first movement over the connecting region (250) and a second movement which is superposed on the first movement and which differs from the first movement, and wherein, by means of the second movement, melt bath dynamics are influenced in targeted fashion and/or a vapour capillary that forms is modified in targeted fashion.

Description

description

Method for connecting pipes of a tube bundle heat exchanger with a

Tube bottom of the tube bundle heat exchanger

The invention relates to a method for connecting pipes of a

Tube bundle heat exchanger with a tube plate of the tube bundle heat exchanger and a device for its implementation.

Prior art tube bundle heat exchangers are configured to transfer heat from a first fluid to a second fluid. For this purpose, a

Shell and tube heat exchanger usually a hollow cylinder, in the interior of a plurality of tubes is arranged. One of the two fluids can be passed through the tubes, the other fluid through the hollow cylinder, in particular around the tubes. The tubes are secured with their ends along their circumference to tubesheets of the tube bundle heat exchanger.

In the course of the production process of a tube bundle heat exchanger, the tubes are connected with their ends, for example, materially bonded to the tube sheets. Depending on the number of tubes, up to several tens of thousands of tube-tubesheet connections are produced.

From DE 10 2006 031 606 A1 a method for laser welding is known in which the feed movement of the laser beam is superimposed on a pendulum motion. This pendulum movement takes place substantially in the direction perpendicular to the feed direction. The pendulum movement takes place here for reasons of better Spaltüberbrückbarkeit.

It is desirable to provide a way to order a pipe

Tube bundle heat exchanger with a tube plate of the tube bundle heat exchanger in a low-cost and cost-effective manner to connect with each other in high quality. Disclosure of the invention

According to the invention, a method for connecting pipes of a

Tube bundle heat exchanger with a tube plate of the tube bundle heat exchanger and a device for its implementation with the features of the independent claims proposed. Advantageous embodiments are the subject of the dependent claims and the following description. Embodiments and advantages of the method according to the invention and the device according to the invention will become apparent from the following description in an analogous manner.

The tubes are connected by means of laser welding to the tube bottom cohesively. In the course of laser welding, a laser beam is generated and focused on a point to be welded in a connection region between the tube and tube sheet. In this connection region, the corresponding tube is to be materially connected to the tube sheet. A corresponding weld between tube and tube sheet is created in this connection area.

The focused laser beam is in accordance with a first movement, or a

Main motion or feed motion, moving across the connection area. This first movement takes place in particular along a first direction (feed direction) over the connection region. This first direction corresponds in particular to a main extension direction of the to be generated

Weld. This first movement of the laser beam is superimposed on a second movement, in particular a so-called overlay movement, which is different from the first movement. In particular, this second movement takes place along a second direction, which is in particular different from the first direction.

In particular, an oscillation movement may be performed as this second movement. To connect the individual tubes with the tubesheet, is

According to the invention, a laser welding is thus carried out, in which two movements of the laser beam are superimposed in the sense of the vector geometry.

Appropriately, a so-called laser welding can be carried out with beam oscillation. In addition, according to the invention, the molten bath and its properties are flexibly influenced by the second movement. In particular, a molten bath dynamics can be flexibly influenced in a targeted manner and / or a resulting vapor capillary can be purposefully modified, for example to form an elongated or oval shape. Due to such an altered melt pool dynamics or such a modification of the vapor capillary, in particular outgassing can be promoted. Potential contamination in a gap between the pipe and the tube sheet can lead to the risk of porosity in the weld metal. By influencing the molten bath dynamics and the modification of the vapor capillary, this danger can be greatly reduced.

For the above-mentioned change in the melt-bath dynamics or the modification of the vapor capillary, the second movement is in particular a circular or elliptical movement, in which case transverse deflections of 0.15-0.25 mm, in particular 0.23 mm, and longitudinal deflections of 0.15, 0.25 mm, in particular 0.23 mm, are particularly advantageous. The preferred frequency of the second movement is 3000-4500 Hz, in particular 3500 Hz.

It should be emphasized at this point that the superimposition of the two movements in the present invention is used less for better Spaltüberbrückbarkeit than for purposes of pore reduction.

In this context, laser welding or laser beam welding is to be understood in particular to mean a process as described in DIN EN ISO 4063

("Welding and Related Processes - List of Processes and Order Numbers") is defined as Process 52. In this case, energy is introduced by a laser beam into workpieces to be joined.

In the course of laser welding, the laser beam is generated by a suitable laser, for example by a C0 ₂ laser, CO laser, solid-state laser, in particular Nd: YAG laser, Nd glass laser, Erbium YAG laser, disk laser, fiber laser and / or diode lasers. The generated laser beam is guided through optical elements such as lenses and / or mirrors, eg concave mirrors, and focused on a point to be welded in the connection region.

The laser welding apparatus according to the invention is for connecting pipes of a shell-and-tube heat exchanger to a tube bottom of the tube

Shell and tube heat exchanger configured accordingly and has a laser for generating a laser beam, a first control device for driving a first traversing mechanism for generating a first movement of the laser beam and a second control device for controlling a second movement mechanism for generating a second movement of the laser beam, wherein the first and the second control device are adapted to perform a method according to the invention. Here, the first and the second control unit can be accommodated combined in a common control unit. It may also be expedient to combine the first and the second travel mechanism into a common movement mechanism. A separation into a first and a second control device and a first and a second movement mechanism is

especially useful if an existing device for laser welding to be retrofitted to perform an inventive method.

The device according to the invention for laser welding or a corresponding laser welding device has in particular the laser and a suitable housing in which the optical elements are arranged. The laser can also be arranged in this housing or outside of the same, wherein the

Laser beam is coupled in this case in the housing. For example, several or all optical elements may be arranged in a laser head. The laser beam is coupled into this laser head. The first and second movement of the laser beam and thus the production of the tube-tube-ground connection can be carried out by a suitable automated control. The laser welding with beam oscillation can thus be carried out automatically in a simple manner, in particular. The

automated control controls in particular expedient elements of

Laser welding apparatus to focus the laser beam and move accordingly.

The focused laser beam strikes the spot to be welded in the

Connection area on. The respective tube and / or the tubesheet are melted in an area around this point to be welded, whereby the molten bath is generated.

A special embodiment of the laser welding is the so-called deep welding. In this case, the intensity of the laser beam generated is above a predetermined limit, for example above a limit of 1 MW / cm ² , 2 MW / cm ² or 4 MW / cm ² . Due to this comparatively high intensity, a part of the

Material in the molten bath, whereby a metal vapor is generated. By further absorption of the laser energy of this metal vapor is at least partially ionized, whereby a laser-induced plasma or metal vapor plasma is generated. Due to the high intensity of the laser beam, a melt continues to form in the melt

Welding capillary or vapor capillary, which is also referred to as "keyhole". This vapor capillary is formed as a cavity, which with the

Metal vapor plasma is filled. Since the degree of absorption of the metal vapor plasma is, in particular, higher than the degree of absorption of the melt, the energy of the laser beam can be introduced almost completely into the respective tube or the tubesheet.

When the laser beam is moved over the connection area, the running

molten material behind the laser beam together and solidifies to the weld. In the course of the main movement, the laser beam is moved along the first direction to connect the respective tube along its circumference to the tubesheet and thus to produce the corresponding weld around the tube. The main movement thus represents in particular a circular movement around the tube or along its circumference.

In particular, at high powers of the laser beam, it may prove difficult to guide the laser beam precisely along points in the connection area at which tube and tube sheet touch, and to produce the molten bath precisely along these points. Would not be a superposition movement

be carried out and the melt would be used exclusively in the course of

Therefore, a precise generation of the molten bath can prove difficult.

Due to the additional second movement or overlay movement, which is superimposed on the main movement, the molten bath can be produced with greater flexibility. Due to this superimposed second movement, it is not exclusively important to direct the laser beam in the course of the main movement as precisely as possible to defined points in the connection area and to move as exactly along the first direction as possible. Instead, the laser beam can be moved in particular over an extended, wide area around these corresponding points or be oscillated. Due to the superimposition movement, a broader melting bath or a wider melting area can be generated in a simple manner than would be possible in the course of the main movement. In particular, additional degrees of freedom thus result in order to direct the laser beam onto the connection region and to produce the molten bath.

In particular, it does not have a negative effect on the connection to be made between tube and tubesheet when the laser beam in the course of the main and / or

Overlapping movement can not be performed absolutely accurately along a respective predetermined path and thus not absolutely exactly along the respective direction. In a pure main motion, this would be much more important, because there the melt is generated exclusively by the main movement. If, on the other hand, a broad molten bath is produced by the combination of main and overlay movement, slight deviations of the individual movements from the given given path are not or hardly significant and do not adversely affect the molten bath and the connection to be produced.

By the first movement advantageously the main extension direction of the weld or the molten bath is specified. The first movement thus runs, in particular, along the points at which the pipe and the tube bottom touch, in particular along the connection region or along a connecting region

Main extension direction of the connection area.

Preferably, the width of the weld seam or of the molten bath is predetermined by the second movement, that is to say in particular an expansion of the weld seam or of the molten bath perpendicular to the first direction of movement or perpendicular to the main extension direction of the weld seam. In particular, the width of the weld seam or of the molten bath may be deliberately influenced by the second movement and in particular set to a predetermined value.

According to an advantageous embodiment, the first movement and / or the second movement by movement of individual optical elements in one

Beam path of the laser beam generated. Individual optical elements, in particular mirrors, can be displaced, pivoted, rotated and / or tilted for this purpose become. In particular, a first mirror can be provided which can be rotated or tilted about a first axis, for example about a vertical axis, and furthermore a second mirror can be provided which is rotatable about a second axis. This second axis may in particular run perpendicular to the first axis and, for example, be a horizontal axis.

Alternatively or additionally, the first movement and / or the second movement can advantageously be generated by moving a device for laser welding or a part of a device for laser welding. This part or the entire laser welding device may e.g. by means of a mechanical

Traversing be moved accordingly, in particular moved, pivoted, rotated and / or tilted. In the course of this, for example, a system of several optical elements can be moved together.

For example, several or all optical elements can be arranged in the laser head and this laser head can be moved in particular. Thus, in particular, a plurality of optical elements can be moved together to produce the main and / or overlay movement.

According to an advantageous embodiment, the first movement can be generated by moving a part of the laser welding device, preferably a part in which a plurality of optical elements are arranged, e.g. the laser head, and the second movement can be generated by moving individual optical elements in this part of the laser welding apparatus. The main and the

Superposition movement are thus generated in each case in particular by means of different mechanisms. The corresponding part of the laser welding device and the corresponding individual optical elements can be driven in this case, in particular independently of each other, to the two movements of the

Overlap laser beam. Preferably, the first movement is a circular movement whose radius substantially or completely corresponds to the radius of a pipe. As already explained above, the first movement thus preferably runs in a circle around the tube or along its circumference. The first direction is thus in particular tangential to the circumference of the tube. The second movement is preferably a circular and / or elliptical movement (oscillation movement). The radius or the lateral extent of this

Oscillation movement should be smaller than the radius of the main movement, for example by a factor of 5, 10, 15 or above. The second movement may alternatively or additionally preferably be a translatory movement perpendicular to the first movement, the direction of this second movement reversing alternately.

Preferably, the tubes and / or the tubesheet are each made of steel or a non-ferrous metal. In this context, steel is to be understood as meaning, in particular, a material according to DIN EN 10020: 2000-07, namely a material whose mass fraction of iron is greater than that of any other element whose carbon content is generally less than 2% and the other A limited number of chromium steels can contain more than 2% carbon, but 2% is the usual limit between steel and cast iron. " Non-ferrous metal is generally understood to mean a metallic material that is not iron.

In particular, in pipes and / or tubesheet made of steel or non-ferrous metals in the presence of contamination in a gap between the pipe and

Pipe soil the danger of the emergence of porosity by favoring the

Outgassing greatly reduced due to altered melt dynamics and / or modification of the Dampfbadkapillare towards an oval or elongated shape.

Advantageously, the tubes and / or the tubesheet are each made of aluminum or an aluminum alloy. By such use of a

Aluminum material, so of aluminum or an aluminum alloy, the tube bundle heat exchanger can be built in particular much easier than a shell-and-tube heat exchanger made of other materials, such as steel, stainless steel or chrome-nickel steel. The tube bundle heat exchanger from a

In particular, aluminum material is up to 50% lower in mass than a corresponding shell and tube heat exchanger, e.g. made of chrome-nickel steel.

For the processing of pipe or tube sheet made of an aluminum material, it should be noted that aluminum reacts quickly with oxygen, resulting in

Alumina Al ₂ 0 ₃ on the respective workpiece, ie on the pipe and / or the Tube sheet, forming. On the workpieces to be welded thus forming an oxide layer, which in particular is to be broken or melted. Only when this oxide layer has been broken, sufficient energy can be introduced into the workpieces. This oxide layer usually has a much higher melting point than the underlying workpiece, ie as the lying below the oxide layer part of the tube or the tube sheet. For example, the oxide layer may have a melting point between 2000 ° C and 2100 ° C, in particular substantially 2050 ° C. Depending on the exact composition, however, the underlying workpiece may have a melting point between 500 ° C and 700 ° C, in particular between 550 ° C and 660 ° C.

By laser welding, this oxide layer can be broken and in particular completely melted, since in laser welding in particular a comparatively high energy concentration can be achieved by the laser beam. It can be particularly effective energy introduced into the underlying workpiece. Tubes and tubesheet made of an aluminum material can thus be connected to each other in a particularly effective, low-cost and cost-effective manner by laser welding. Conventional welding processes are only of limited use for welding pipes and tubesheet from an aluminum material, since it is usually not possible to sufficiently melt the complete oxide layer. Non-molten oxides of the oxide layer remain in the weld metal, which is referred to as oxide flags. Such oxide lugs represent a clear separation or defect in the weld metal and in the weld. By laser welding, the formation of such oxide lances can be prevented and a clean, pure compound or

Weld can be generated without such defects.

Advantageously, an additional material can be supplied in the course of the laser welding. Preferably, a protective gas or process gas can be supplied, preferably argon, helium, nitrogen, carbon dioxide, oxygen or a mixture of these gases mentioned. The laser welding can be carried out expediently but also without supply of protective gas and / or filler material. The tube bundle heat exchanger to be produced, in particular, has a multiplicity of tubes in its finished, ready-to-operate state

for example, can be arranged inside a hollow cylinder. Of the

Tube bundle heat exchanger can have several hundred, several thousand or even several tens of thousands of tubes. Furthermore, in particular at least one tubesheet is provided in the fabricated tube bundle heat exchanger, which may be formed, for example, as a plate. The tubes are connected at their ends along their circumference fixed to this tube sheet or with these tubesheets. The tubesheet has in particular holes or holes, which correspond in diameter to the diameters of the tubes. In particular, each tube is fastened with one of its ends in each case to one of these bores.

In the course of manufacturing the tube bundle heat exchanger, the tubes are placed inside the tube bundle heat exchanger and aligned as desired.

Then the tubes with the tubesheet or tube sheets

cohesively connected by laser welding with beam oscillation. In the course of production in this way, in particular up to 25,000 tube-tube bottom connections are produced by means of laser welding. If all pipes with the

Tubular soil were joined cohesively, a jacket can be arranged around the tubes, which forms the hollow cylinder.

Advantageously, pipes are connected to the tube sheet of a straight tube heat exchanger. The tubes of such a straight tube heat exchanger extend in a straight line inside the hollow cylinder. In this case, in particular two tube sheets are provided, which on

can be arranged opposite ends of the straight tube heat exchanger. Each tube is in each case connected to one of these two tube sheets in a material-bonded manner with one of its ends in each case. Preferably, pipes with the tube sheet of a U-tube heat exchanger can be connected to each other. The tubes of such a U-tube heat exchanger extend within the hollow cylinder in particular U-shaped. Such a

Heat exchanger may in particular have only one tube bottom. Since the tubes are bent in this case U-shaped, they can each with its two ends be attached to the same tube sheet. It is also conceivable to use two juxtaposed tube plates.

Preferably also tubes and tube sheets of a wound

Tube bundle heat exchanger to be interconnected. In this type of coiled-tube heat exchanger, in particular, the tubes are wound inside the hollow cylinder, i. in particular, the tubes extend in a circular or spiral manner about an axis, in particular about a longitudinal axis or main expansion axis of the tube bundle heat exchanger. In particular, a core tube can be provided in the interior of the hollow cylinder around which the tubes are arranged in a circle or spiral around. Such a coiled tube bundle heat exchanger in particular has two tube plates arranged at opposite ends.

By laser welding the tube-tube bottom connections, moreover, further advantages can be achieved. In laser welding, a comparatively high welding speed can be achieved, as a result of which the pipe-tube-bottom connections can be produced particularly quickly and efficiently. Furthermore, by means of laser welding reproducible tube-tube bottom joints can be produced with uniform quality. In particular, at

Laser welding comparatively narrow welds are generated, which can be avoided that affect welds adjacent pipes.

The comparatively thick tubesheet (in particular in comparison to the wall thicknesses of the tubes) has in particular a comparatively high thermal conductivity, so that introduced heat is dissipated very quickly. Conversely, the comparatively thin or thin-walled tubes expediently have a comparatively low thermal conductivity, so that introduced heat can not be dissipated quickly. By laser welding sufficient energy can be introduced into the tubesheet to melt this despite its relatively high thermal conductivity. Nevertheless, it can be ensured that the pipes are not prematurely melted back.

Further advantages and embodiments of the invention will become apparent from the

Description and attached drawing. It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically with reference to an embodiment in the drawing and will be described in detail below with reference to the drawing. Brief description of the drawings

Figure 1 shows schematically a preferred embodiment of a

Tube bundle heat exchanger, which was manufactured by means of a preferred embodiment of a method according to the invention.

Figure 2 shows schematically a preferred embodiment of a device according to the invention, which is adapted to carry out a preferred embodiment of a method according to the invention. Figure 3 shows schematically a part of a preferred embodiment of a

Device according to the invention, which is adapted to carry out a preferred embodiment of a method according to the invention.

FIG. 4 schematically shows a part of a shell-and-tube heat exchanger which is processed in the course of a preferred embodiment of a method according to the invention.

EMBODIMENT (S) OF THE INVENTION FIG. 1 schematically shows a preferred embodiment of a shell-and-tube heat exchanger 100 in the form of a wound shell-and-tube heat exchanger which has been produced by means of a preferred embodiment of a method according to the invention. In Figure 1 a, the tube bundle heat exchanger 100 is shown in a sectional view. The shell-and-tube heat exchanger 100 has a jacket 110 which has a fluid inlet 11 and a fluid outlet 12 to guide a first fluid through the jacket 110.

Within the shell 1 10 a tube bundle 120 is arranged from a plurality of tubes 121. Through the tubes 121, a second fluid can be passed. The tubes 121 are spirally wound around a core tube 140. The individual tubes 121 are connected cohesively to tube plates 130 of the heat exchanger 100.

The tube plates 130 have bore regions 131 along their circumference

Bores 132, wherein each of the tubes 121 of the tube bundle 120 is connected to one of these bores 132 cohesively with the respective tube plate 130. The heat exchanger 100, the tubes 121 and the tubesheets 130 are made of, for example, an aluminum alloy, e.g. from an aluminum-magnesium-manganese alloy.

In Figure 1 b is a part of the wound tube heat exchanger 100 (the

Tube bundle 120, the tube plates 130 and the core tube 140) of Figure 1 a shown in a perspective view. As can be seen in Figure 1 b, the

Tube sheets 130, for example, attached to the core tube 140 via support arms 133.

In order to connect each of the tubes 121 to one of the bores 132 in a material-locking manner with the respective tubesheet 130, these cohesive tubesheet-tube connections are produced in the course of a preferred embodiment of the method according to the invention by laser welding with beam oscillation.

2 shows schematically a preferred embodiment of a device 200 according to the invention for laser welding, which is adapted to such a preferred embodiment of the method according to the invention

perform. FIG. 2 shows by way of example how, with this laser welding apparatus 200, one of the tubes, designated by 125 in FIG. 2, with one of the tubesheets 130 of the wound tube bundle heat exchanger 100 according to FIG

Manufacturing process can be materially connected. The laser welding apparatus 200 has a laser 210, for example a NckYAG laser, and a laser head 220. The laser 210 generates a laser beam 21 1, which is coupled into the laser head 220. In the laser head 220 expedient optical elements are arranged to focus the laser beam 21 1 on a point to be welded in a connecting region 250 between the tube 125 and the tube plate 130.

The focused laser beam 21 1 impinges on the spot to be welded in the

Connection region 250, whereby the tube 125 and the tube sheet 130 are at least partially melted, so that a molten bath 253 is formed. When the laser beam is moved over the connection area, the running

molten material behind the laser beam together and solidifies to the weld 260.

The laser welding apparatus 200 further includes a first controller 230 and a first traversing mechanism 231 for generating a first movement of the laser beam 21 1. The movement mechanism 231 is suitably activated for this purpose by the first control unit 230.

By means of the movement mechanism 231, in particular the entire

Laser welder 200, in particular both the laser 210 and the laser head 220 together, are moved. In the course of this, the laser welding apparatus 200 can be rotated, for example, both about a z-axis and about an x-axis.

The tube plate 130 extends, for example, in a plane spanned by the x-axis and a y-axis, wherein the z-axis is oriented perpendicular to this plane. According to this first movement or main movement, the laser beam 21 1 is moved over the connection area along a first direction 251. This first direction 251 corresponds in particular to a main extension direction of the

Connection area or a main extension direction of the generated

Weld 260. Furthermore, this first direction 251 extends in particular parallel to a circumference 252 of the tube 125. Furthermore, a second control device 240 and a second displacement mechanism are provided to produce a second movement of the laser beam 21 1. The second movement mechanism will be explained in detail below with reference to FIG. It should be noted that the first controller 230 and the second controller 240 may be housed in a common control unit combined. The same applies to the two travel mechanisms.

By means of the second movement mechanism, individual optical elements can be moved in the laser head 220, whereby a second movement is superimposed on the first movement of the laser beam 21 1. This second movement will be explained in detail below with reference to FIG.

FIG. 3 schematically shows the laser head 220 from FIG. 2 in a sectional view. The laser beam 21 1 generated by the laser 210 is coupled into the laser head through a lens 221 and initially strikes a deflection mirror 222 in this example. The laser beam 21 1 then encounters a first rotatable mirror 223 and then a second rotatable mirror 226. Subsequently, the laser beam 21 1 hits a focusing lens 229, after which it leaves the laser head.

The rotatable mirrors 223 and 226 may each be formed, for example, as a concave mirror. The first mirror 223 may be rotated about a first axis 225 by a first adjustment mechanism 224. The second mirror 226 may be rotated about a second axis 228 by a second adjustment mechanism 227. The axes 225 and 228 are in particular perpendicular to each other. The

Adjustment mechanisms 224 and 227 together form the above-explained second movement mechanism for generating the second movement of the laser beam 21 1.

The second controller 240 for this purpose controls the adjustment mechanisms 224 and 227 to rotate the rotatable mirrors 223 and 226, respectively, to superimpose the second movement of the laser beam 21 1 of the first movement.

In Figure 4, examples of the first and the second movement of the laser beam are shown schematically, which can be carried out in the course of a preferred embodiment of a method according to the invention. In Figures 4a to 4e In each case, the tube 125 and a part of the tube plate 130 are shown schematically in a plan view.

FIG. 4 a shows schematically an example of the first movement of the laser beam 21 1. The first movement thereby runs in the connection region 250 along the circumference 252 of the tube 125. The first movement is thus a circular movement about the center of the tube 125, the first direction of movement 251 runs parallel to the circumference 252 of the tube 125. A radius 301 of this circular movement corresponds to, for example, the outer radius of the tube 125th

FIG. 4b schematically illustrates an example of the second movement of the laser beam 21 1. The second movement is also a circular motion in this example. The diameter 302 of this circular movement in this example corresponds to a width of the connecting region 250. In particular, the diameter 301 of this circular movement also corresponds to the width of the weld 260.

The second movement may, for example, also be elliptical, as shown in FIG. 4c. For example, in this example, twice the length of the semi-minor axis 303 corresponds to the corresponding ellipse of the width of the

Connecting region 250 and further in particular the width of the weld 260.

In Fig. 4d, an example of the movement of the laser beam 21 1 as a

Superposition of the first movement according to Figure 4a and the second movement shown in Figure 4b schematically. The laser beam 21 1 is over the

Connection area 250 thus moves as a superposition of a circular movement with radius 301 and a circular movement with diameter 302. The center of the second movement in the form of the circular movement according to FIG. 4b lies, for example, on the circumference 252 of the tube 125. For a positive influence on the melt-bath dynamics and a targeted flow

Modification of the resulting vapor capillary during laser welding, in particular during deep welding with comparatively high laser beam intensities (see the corresponding explanations above in the description) becomes the second

Movement made with a transverse deflection between 0.15 and 0.25 mm and a longitudinal deflection of 0.15 to 0.25 mm. Is the longitudinal and equaling the transverse deflection, there is a circular second movement, otherwise an elliptical second movement is obtained. A circular second movement with a transverse and longitudinal deflection of 0.23 mm has proven to be particularly advantageous. The frequency of this second movement is in the range of 3000-4500 Hz, in particular a frequency of 3500 Hz is particularly advantageous. In this way, the risk of porosity in the welded joint can be greatly reduced by the second movement.

FIG. 4e shows an example of a manufactured tube / tube bottom connection. As a result of the movement of the laser beam 21 1 according to FIG. 4 d, the tube 125 and the tubesheet 130 are melted, in particular over the entire width of the connection region. After the melt has solidified, thus, the weld 260 was generated, wherein the width of the weld 260 of the width of the

Connection area 250 corresponds.

LIST OF REFERENCES

100 shell and tube heat exchangers, wound shell and tube heat exchangers

1 10 coat

1 1 1 fluid inlet

1 12 fluid output

120 tube bundles

121 pipes

125 pipe

130 tube sheets

131 bore area

132 holes

133 support arms

140 core raw r

200 Laser welding machine, apparatus for laser welding

210 Laser, Nd: YAG laser

2 laser beam

220 laser head

221 lens

222 deflecting mirror

223 first rotatable mirror, concave mirror

224 first adjustment mechanism

225 first axis

226 second rotatable mirror, concave mirror

227 second adjustment mechanism

228 second axis

229 focusing lens

230 first control unit

231 first movement mechanism

240 second control unit

250 connection area

251 first direction; Main extension direction of the weld

252 circumference of the tube 125

253 molten bath

260 weld Radius of the circular first movement

Diameter of the circular second movement Small semi-axis of the elliptical second movement

Claims

claims

Method for connecting pipes (121, 125) of a

Tube bundle heat exchanger (100) with a tube bottom (130) of the

Tube bundle heat exchanger (100),

- Wherein the tubes (121, 125) by means of laser welding to the tube bottom (130) are integrally connected, in the course of which a laser beam (21 1) generated and to a point to be welded in a connecting region (250) between the tube (125) and tubesheet (130) is focused

- wherein the laser beam (21 1) is moved so that it carries out a first movement over the connecting region (250) and a second movement superimposed on the first movement, which is different from the first movement and

- Being influenced by the second movement a molten bath dynamics targeted and / or a resulting vapor capillary is selectively modified. The method of claim 1, wherein the resulting vapor capillary to a

elongated or oval shape is modified.

A method according to claim 1 or 2, wherein a first movement is achieved by the first movement

Main extension direction (251) of a weld (260) is specified and / or wherein by the second movement, a width (302) of the weld (260) is specified.

4. Method according to one of the preceding claims, wherein the first movement and / or the second movement are produced by movement of individual optical elements (223, 226) in a beam path of the laser beam (21 1). The method of claim 4, wherein at least one mirror (223, 226) in the

Beam path of the laser beam (21 1) is rotated.

Method according to one of the preceding claims, wherein the first movement and / or the second movement are generated by a device for Laser welding (200) or a part of a device for laser welding (200) is moved.

7. The method of claim 6, wherein a laser head (220) of the device for

Laser welding (200) is moved.

A method according to any one of the preceding claims, wherein the first movement is a circular movement whose radius (301) is substantially or entirely equal to the radius of a pipe (125).

9. The method according to any one of the preceding claims, wherein the second movement is a circular and / or elliptical and / or translational in their direction alternating movement. 10. The method of claim 9, wherein the second movement with a transverse deflection of 0.15 - 0.25 mm, in particular 0.23 mm, and / or with a longitudinal deflection of 0.15 - 0.25 mm, in particular 0 , 23 mm, is made. 1 1. A method according to claim 9 or 10, wherein the second movement comprises a

Frequency of 3000 - 4500 Hz, in particular 3500 Hz takes place.

12. The method according to any one of the preceding claims, wherein the tubes (121) and / or the tube sheet (130) are each made of steel or a non-ferrous metal and / or each made of aluminum or an aluminum alloy.

13. The method according to any one of the preceding claims, wherein the tubes (121) and the tube plate (130) of a straight tube heat exchanger, a U-tube heat exchanger or a wound tube bundle heat exchanger (100) are interconnected.

14. The method according to any one of the preceding claims, wherein the laser beam (21 1) by a C0 ₂ laser, CO laser, solid-state laser, Nd: YAG laser (210), Nd glass laser, Erbium YAG laser, Disk laser, fiber laser and / or diode laser is generated.

A laser welding apparatus (200) for connecting pipes (121, 125) of a shell - and - tube heat exchanger (100) to a tube bottom (130) of the

Shell and tube heat exchanger (100) is arranged, wherein the device (200) comprises a laser (210) for generating a laser beam (21 1), a first control device

(230) for driving a first traversing mechanism (231) for generating a first movement of the laser beam (21 1) and a second control device (240) for driving a second traversing mechanism for generating a second movement of the laser beam (21 1), wherein the first and the second controller (230, 240) are adapted to perform a method according to any one of the preceding claims.